Disk drives are information storage devices that use magnetic media to store data. A conventional disk drive comprises a magnetic disk having concentric magnetic tracks formed thereon, a HGA, and a drive arm that drives the HGA. The disk is mounted to a spindle motor, which causes the disk to spin. A voice-coil motor (VCM) controls the motion of the drive arm, which in turn controls the movement of the HGA, and then controls the slider to move from track to track across the surface of the disk for reading data from or writing data to the disk.
However, because of inherent tolerance resulting from the VCM and the suspension, the slider does not attain precise positional control during its displacement. This will affect data reading/writing of the slider.
To solve the above-mentioned problem, piezoelectric (PZT) micro-actuators are employed to modify the displacement of the slider. That is, the PZT micro-actuator corrects the displacement of the slider in a much smaller scale to compensate for the tolerance caused by the VCM and the suspension. The PZT micro-actuator enables a smaller recording track width, hence increasing the “tracks per inch (TPI)” value by 50%. It also reduces the head seeking and settling time, increases the disk surface recording density, and improves drive performance of the disk drive.
Referring to FIGS. 1a and 1b, a traditional HGA 277 comprises a slider 203, a PZT micro-actuator 205, and a suspension 213 to load the micro-actuator 205 and a suspension 213. The PZT micro-actuator 205 comprises a U-shaped ceramic frame 297 having two spaced beams 207 on both sides of which two PZT elements (not labeled) are mounted. The PZT micro-actuator 205 is mounted to a suspension 213 of the HGA 277. The suspension 213 comprises conductive traces 210 that are connected to the micro-actuator 205 by a plurality of electrical connection balls 209, such as gold ball bonding (GBB) and solder ball bonding (SBB), on both sides of the frame 297 next to each beam 207. In addition, a plurality of metal balls 208, such as GBB and SBB, electrically connect the slider 203 to the conductive traces 210.
Also referring to FIG. 1c, the slider 203 is positioned in the micro-actuator 205 between the beams 207. The slider 203 is bonded to the beams 207 at two points 206 by epoxy dots 212 whereby the slider 203 is movable in unison with the beams 207. When power is supplied through the traces 210, the PZT elements of the micro-actuator 205 expand or contact, causing the beams 207 to deform and thus moving the slider 203 on the tracks of the disk. Thus, a fine head position adjustment of the slider 203 can be attained.
However, since the PZT micro-actuator 205 and the slider 203 are mounted to a suspension tongue (not labeled), the PZT micro-actuator 205, when excited, undergoes pure translation, which sways the slider 203 due to the constraint imposed by the U-shaped frame 297 of the micro-actuator 205 and causes a suspension vibration resonance having a frequency the same as the suspension base plate exciting. This limits the servo bandwidth and capacity improvement of hard disk drive.
Thus, it is desired to provide a micro-actuator, a HGA and a disk drive to solve the above-mentioned problems.